The invention is related to known hinge pins for joining the free ends of conveyor belts, such as U.S. Pat. No. 4,023,239. While it is recognized that the placing of sleeves on a wire rope type cable reduces frictional wear on the cable, shear forces are still exerted on the cable due to each sleeve being loaded from only one direction. In addition, known art that involves sleeves to be placed on a wire rope results in expensive hinge pins due to the special configuration previously assumed to be required.
A common failure mode of known mechanical splices is the breaking of the outer wires of the wire rope due to frictional wear and shear forces exerted by the mechanical splice hinge eye elements. Due to these unbalanced shear forces the internal cable will be loaded and as a result will fail by fraying. It should be noted that cable as commonly found in hinge pins is clearly designed for strength in tension, not in shear. A frayed wire rope cannot easily be removed from the mechanical splice. It is therefore typical that the entire mechanical splice is cut out of the belt and a new one installed, involving costly down time for the conveying system and often loss of a functional mechanical splice.
Due to the large volume of coal or product on the conveyor belts and the high speed at which it is being conveyed, it is necessary that the splice be inspected and replaced prior to failure. This pending failure is not easily detected when the wear is internal, as found in known hinge pins. The provision to detect wear on the hinge pin is further emphasized when a means of easily installing or removing the hinge pin is provided.
Objects of the present invention are to solve the problems of:
1. short hinge pin life by making the hinge pin bushing wall, or bearing surface, substantially thick and the flexible wire rope substantially narrow; PA1 2. shear loading forces on the wire rope by placing all shear forces on the hinge pin bushings in a balanced manner; PA1 3. frictional wear on the wire rope, by allowing the hinge pin bushings to rotate freely about the wire rope by a bore in the bushings, through which the wire rope passes, sufficiently larger than the wire rope; PA1 4. aligning, installing and removing the hinge pin is solved by providing a hinge pin tool which can be easily inserted in the mechanical splice and which mechanically attaches to the hinge pin; PA1 5. relative high cost of hinge pins, by employing a hinge pin bushing design that can be manufactured at high rates of speed on a common multi-spindle screw machine; PA1 6. pressure outward on the hinge pin termination bushings commonly generated by the hinge pin bushings, by proper spacing between the hinge pin bushings; and PA1 7. hinge pins drifting laterally within the mechanical splice hinge eye elements, by securing retaining rings or washers to the ends of the hinge pin.